Field of the Invention
The invention relates to an assembly having a honeycomb body which is disposed in the interior of a tubular casing and through which a fluid can flow. The honeycomb body can function in particular as a carrier body for a catalytically active material which permits conversion of harmful components of exhaust gases of an internal combustion engine into harmless substances.
German Utility Model U 89 05 415.6 discloses a metal honeycomb body which serves as a catalyst carrier body and which is disposed in the interior of a tubular casing. The tubular casing has a peripherally extending outwardly flanged portion. It can be inserted into an opening in a wall, which is slightly larger than the outside dimensions of the tubular casing in the region which is not outwardly flanged, until the outwardly flanged portion bears against the edge of the opening. In that position the tubular casing can be connected to the wall by a procedure involving intimate joining of the materials involved so that the tubular casing is durably fixed in position.
German Published, Non-Prosecuted Patent Application DE 42 31 338 A1 discloses a brazing process in which an adhesive material and brazing powder adhering thereto are applied to the outer periphery of the honeycomb body for the purposes of brazing a metal honeycomb body to a tubular casing. By virtue of the adhesive material, the brazing powder continues to cling in position even during the subsequent steps in the process until the brazed join is definitively finished. The process permits the deliberate and specific soldering of partial regions to the outer periphery of a metal honeycomb body.
German Utility Model U 89 10 107.3 discloses a tubular casing for a metal honeycomb body which-has a plurality of external beads or corrugations. The external beads serve to stiffen the tubular casing so that, in comparison with tubular casings without stiffening elements, it is possible to save on materials by virtue of the wall thickness being reduced. The external beads or corrugations serve in particular to prevent the tubular casing from bulging out under load, for example due to gas pressure in the interior of the tubular casing.
European Patent 0 245 737 B1 describes a honeycomb body which is connected to a tubular casing by weld seams extending substantially in the peripheral direction of the tubular casing, in the interior of the tubular casing. By virtue of a suitable choice of welding parameters, it is possible to provide for the roots of the weld seams to sink somewhat inwardly so that in addition there is a form-locking connection between the tubular casing and the honeycomb body. It is generally known that weld seams can be weak locations in a metal structure, which have a tendency in particular toward brittle fracture. Care is therefore to be taken to ensure suitable positioning of weld joins and the choice of a suitable welding process.
German Published, Non-Prosecuted Patent Application DE 41 12 354 A1 discloses a honeycomb body which includes a plurality of layers of corrugated sheet metal layers or smooth and corrugated sheet metal layers and which is connected by welding to a tubular casing disposed around it. In order to facilitate the welding operation and in order to produce a durable connection between the tubular casing and the honeycomb body, the outer layer portion of the honeycomb body is formed from a plurality of mutually overlapping smooth end portions of the corrugated sheet metal layers or the corrugated and smooth sheet metal layers, wherein the end portions are of approximately equal length and are approximately uniformly distributed over the outer periphery of the honeycomb body. The tubular casing and the honeycomb body are welded together in the region of the axial ends of the tubular casing. In a particular configuration the honeycomb body and the tubular casing are reinforced at the ends by additional holding measures, for example a support ring.
Mechanical vibration in a tubular casing can occur due to different excitation mechanisms. For example, in the case of a tubular casing which is disposed in the exhaust system of an internal combustion engine and in the interior of which a honeycomb body acting as a catalyst carrier body is disposed, transverse vibrations of the tubular casing can occur due to vibration of the internal combustion engine, which is transmitted by way of other parts of the exhaust system. A connection between the tubular casing and the honeycomb body can be damaged or destroyed, particularly when resonance vibration is caused to occur in that respect.
A further possible cause of damage to or destruction of the connection is different thermally induced changes in the dimensions of the honeycomb body and the tubular casing. For that reason German Published, Non-Prosecuted Patent Application DE 195 07 299 A1, corresponding to U.S. application Ser. No. 08/921,817, filed Sep. 2, 1997, proposes making a connection between the honeycomb body and the tubular casing only in a partial region of the axial length of the tubular casing. Preferably, the connecting region is approximately at the center of the axial length of the tubular casing.